Polarization plate for use in a liquid crystal display

ABSTRACT

A polarization plate is provided for use between a light source and a display panel, where the light source is configured to emit light having a plurality of planes of polarization and the display panel is configured to have a predetermined polarization axis. The plate includes a repolarization region and a prepolarization region. The repolarization region is configured to diffuse and to depolarize or rotate at least one plane of polarization of the light passing therethrough. The prepolarization region is disposed adjacent to and in contact with the repolarization region. The prepolarization region is configured to be substantially nonabsorbent, to allow passage of light having a plane of polarization that is substantially aligned with the predetermined polarization axis, and to prevent passage of light having a plane of polarization that is not substantially aligned with the predetermined polarization axis. In another embodiment, an interface is provided between the regions.

TECHNICAL FIELD

The inventive subject matter generally relates to liquid crystaldisplays, and more particularly relates to a polarization plate for usein a liquid crystal display.

BACKGROUND

Conventional liquid crystal displays include a reflective cavity, alight source, a display panel, and a diffuser. The light source ispositioned such that it can inject light into the reflective cavity. Thereflective cavity can take several general forms, such as a reflectivesurface forming one or more sides of an enclosure around the lightsource. Such reflective cavities can include a transparent light guidewhich is illuminated or edge lit along one or more edges. The displaypanel is spaced apart from the reflective cavity and may include a rearpolarizer configured to allow passage of light having a plane ofpolarization that is substantially aligned with a predeterminedpolarization axis. The diffuser is typically disposed between thereflective cavity and the display panel and is configured to enhance theuniformity of light exiting the reflective cavity, including light thathas a plane of polarization that is substantially aligned with thepredetermined polarization axis.

Manufacturers typically incorporate liquid crystal display componentsthat may be capable of optimizing energy usage, while having minimalweight, thickness, and cost. For example, manufacturers traditionallyinclude diffusers formed of thin, highly transmissive materials having asurface texture on one or both sides to enhance light diffusion. Thediffuser is typically placed such that an air gap is maintained betweenthe diffuser and the other display components. The air gap enhances thediffusion properties of the diffuser and in addition reduces thelikelihood of light absorption by non-ideal components in the vicinityof the diffuser. To further enhance energy efficiency, a pre-polarizingthin plastic film may be included that recycles unpassed light forsubsequent passage through the diffuser or reflective cavity. Thepre-polarizing film has conventionally been disposed between thediffuser and the display panel. In some display configurations, thepre-polarizing film specularly reflects light back to the diffuser andthe reflective cavity which then return a portion of the light towardthe display panel such that some of the reflected light becomesreoriented and allows passage of light that is substantially alignedwith the polarization axis of the display panel. In otherconfigurations, the pre-polarizing film backscatters the unpassed lightbut allows passage of light that is substantially aligned with thedisplay panel polarization axis.

Although the above-described configurations have been adequate forsmaller displays, they have exhibited drawbacks. In particular, asliquid crystal display sizes increase the structural integrity ofcertain sections of the film may become difficult to maintain. Forexample, the center of the film may become distorted or mayinadvertently contact other display components when the display isshaken, dropped, or exposed to extreme thermal or humid environments.

One prior art method which can minimize film damage is lamination of aspecular pre-polarizing film to a rear polarizer and applying the two tothe display panel as a single sheet. However, it has been found thatlaminating the two polarizers together may undesirably alter someoptical and physical characteristics of the liquid crystal display andmay not be suitable for certain applications, such as avionics ormilitary purposes. For example, the luminance, viewing angle,uniformity, or environmental performance of the liquid crystal displaymay not meet certain regulations that are set for displays used inavionics or military applications.

Accordingly, it is desirable to have a liquid crystal display thatmaintains structural and environmental integrity when produced in largesizes or used in demanding environments. In addition, it is desirablefor the liquid crystal display to operate efficiently and to produce ahigh luminance that is suitable for use in avionics, militaryapplications and commercial applications. Further, it is desirable forthe liquid crystal display to have a wider illumination and viewingangle as compared to conventional displays. Moreover, it is desirablefor the liquid crystal display to be relatively simple and inexpensiveto manufacture. Furthermore, other desirable features andcharacteristics of the inventive subject matter will become apparentfrom the subsequent detailed description and the appended claims, takenin conjunction with the accompanying drawings and this background.

BRIEF SUMMARY

A component is provided for use between a light source and a displaypanel of a liquid crystal display, the light source configured to emitlight having one or more planes of polarization and the display panelconfigured to have a predetermined polarization axis. Display devicesincluding the component are also provided.

In an embodiment, and by way of example only, the component includes aplate, a repolarization region, and a prepolarization region. The plateincludes a first major surface, a second major surface opposing thefirst major surface, and an edge joining the first and second majorsurfaces. The first major surface is configured to allow a majority ofincident light from the light source to be transmitted therethroughtoward the second major surface. The repolarization region is betweenthe first and second major surfaces and configured to receive a majorityof light transmitted through the first major surface. The repolarizationregion is configured to diffuse and to change polarization or rotate atleast one plane of polarization of the light passing therethrough. Theprepolarization region is formed between the first and second majorsurfaces adjacent to and in contact with the repolarization region. Theprepolarization region is configured to be substantially nonabsorbent,to allow passage of light through the second major surface having aplane of polarization that is substantially aligned with thepredetermined polarization axis, and to prevent passage of light throughthe second major surface having a plane of polarization that is notsubstantially aligned with the predetermined polarization axis. Thelight is not injected between the repolarization region and theprepolarization region and is not injected through the plate edge.

In another embodiment, by way of example only, the component includes aplate, a repolarization region, an interface, and a prepolarizationregion. The plate includes a first major surface, a second major surfaceopposing the first major surface, and an edge joining the first andsecond major surfaces, and the first major surface is configured toallow a majority of incident light from the light source to betransmitted therethrough toward the second major surface. Therepolarization region is between the first and second major surfaces andconfigured to receive a majority of light transmitted through the firstmajor surface. The repolarization region is configured to diffuse and tochange polarization or rotate at least one plane of polarization of thelight passing therethrough. The interface is between the first andsecond major surfaces and has a first side and a second side. Theinterface first side is disposed adjacent to and in contact with therepolarization region. The prepolarization region is formed between thefirst and second major surfaces adjacent to and in contact with theinterface, and is configured to be substantially nonabsorbent, to allowpassage of light through the second major surface having a plane ofpolarization that is substantially aligned with the predeterminedpolarization axis, and to prevent passage of light through the secondmajor surface having a plane of polarization that is not substantiallyaligned with the predetermined polarization axis. The light is notinjected between the repolarization region and the prepolarizationregion or the interface and is not injected through the plate edge.

In another embodiment, by way of example only, a display device includesa light source, a reflective surface, a polarized display panel, and acomponent. The reflective surface is disposed proximate the light sourceand configured to reflect light emitted therefrom. The polarized displaypanel is spaced apart from the reflective surface, the polarized displaypanel having a predetermined polarization axis. The component isdisposed between the reflective surface and the polarized display paneland configured to receive the reflected light. The polarization plateincludes a plate, a repolarization region, and a prepolarization region.The plate includes a first major surface, a second major surfaceopposing the first major surface, and an edge joining the first andsecond major surfaces, and the first major surface is configured toallow a majority of incident light from the light source to betransmitted therethrough toward the second major surface. Therepolarization region is between the first and second major surfaces andconfigured to receive a majority of light transmitted through the firstmajor surface. The repolarization region is configured to diffuse and tochange polarization or rotate at least one plane of polarization of thelight passing therethrough. The prepolarization region is formed betweenthe first and second major surfaces adjacent to and in contact with therepolarization region. The prepolarization region is configured to besubstantially nonabsorbent, to allow passage of light through the secondmajor surface having a plane of polarization that is substantiallyaligned with the predetermined polarization axis, and to prevent passageof light through the second major surface having a plane of polarizationthat is not substantially aligned with the predetermined polarizationaxis. The light is not injected between the repolarization region andthe prepolarization region and is not injected through the plate edge.

In still another embodiment, by way of example only, the display deviceincludes a light source, a reflective surface disposed proximate thelight source and configured to reflect light emitted therefrom, apolarized display panel spaced apart from the reflective surface, thepolarized display panel having a predetermined polarization axis, and acomponent disposed between the reflective surface and the polarizeddisplay panel and configure to receive the reflected diffuse light. Thecomponent includes a plate, a repolarization region, an interface, and aprepolarization region. The plate includes a first major surface, asecond major surface opposing the first major surface, and an edgejoining the first and second major surfaces, and the first major surfaceis configured to allow a majority of incident light from the lightsource to be transmitted therethrough toward the second major surface.The repolarization region is between the first and second major surfacesand configured to receive a majority of light transmitted through thefirst major surface. The repolarization region is configured to diffuseand to change polarization or rotate at least one plane of polarizationof the light passing therethrough. The interface is between the firstand second major surfaces and has a first side and a second side. Theinterface first side is disposed adjacent to and in contact with therepolarization region. The prepolarization region is between the firstand second major surfaces adjacent to and in contact with the interface.The prepolarization region is configured to be substantiallynonabsorbent, to allow passage of light through the second major surfacehaving a plane of polarization that is substantially aligned with thepredetermined polarization axis, and to prevent passage of light throughthe second major surface having a plane of polarization that is notsubstantially aligned with the predetermined polarization axis. Thelight is not injected between the repolarization region and theprepolarization region or the interface and is not injected through theplate edge.

In still yet another embodiment, by way of example only, a componentincludes a plate, a repolarization region, and a prepolarization region.The plate includes a first major surface, a second major surfaceopposing the first major surface, and an edge joining the first andsecond major surfaces, and the first major surface is configured toallow a majority of incident light from the light source to betransmitted therethrough toward the second major surface. Therepolarization region is between the first and second major surfaces andis configured to receive and diffuse light from the light source and todepolarize or rotate at least one plane of polarization of the lightpassing therethrough. The prepolarization region is between the firstand second major surfaces adjacent to and is in contact with therepolarization region. The prepolarization region is configured to besubstantially nonabsorbent, to allow passage of light having a firstpolarization, and to prevent passage of light having a secondpolarization. The light is not injected between the repolarizationregion and the prepolarization region or the interface and is notinjected through the plate edge.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive subject matter will hereinafter be described inconjunction with the following drawing figures, wherein like numeralsdenote like elements, and

FIG. 1 is a simplified cross-sectional view of a display deviceaccording to an embodiment;

FIG. 2 is a cross-sectional view of a polarization plate that may beimplemented into the display device shown in FIG. 1, according to anembodiment;

FIGS. 3-6 are cross-sectional views of prepolarization regions ofseveral polarization plates, according to several embodiments;

FIG. 7 is a cross-sectional view of a polarization plate that may beimplemented into the display device shown in FIG. 1, according toanother embodiment;

FIG. 8 is a simplified illustration of an embodiment of lightpropagating through a polarization plate; and

FIG. 9 is a graph comparing relative luminance measurements obtainedfrom a conventional liquid crystal display and a display including apolarization plate.

DETAILED DESCRIPTION

The following detailed description of the inventive subject matter ismerely exemplary in nature and is not intended to limit the inventivesubject matter or the application and uses of the inventive subjectmatter. Furthermore, there is no intention to be bound by any theorypresented in the preceding background or the following detaileddescription.

Turning now to FIG. 1, a simplified cross-sectional view of a displaydevice 100 is shown according to an embodiment. The display device 100may be any one of numerous types of display devices that operate bypolarizing light in a predetermined direction for display. Examples ofsuitable display devices 100 include liquid crystal display devices,including, but not limited to, active matrix liquid crystal displaydevices, passive matrix liquid crystal display devices, and directlyaddressed liquid crystal display devices.

The display device 100 includes a light source 102, a reflective surface104, a polarized display panel 106, and a polarization plate 108. Thelight source 102 may be in operative communication with a power source(not shown) or may be self-powered. In an embodiment, the light source102 may produce unpolarized light that may be diffuse or direct. Inanother embodiment, the light source 102 may produce light that may bepolarized having a particular orientation. Suitable devices for use asthe light source 102 include, but are not limited to one or morefluorescent lamps, light emitting diodes, incandescent lamps, lasers andelectrical discharge lamps. The light source 102 is disposed such thatat least a portion of light therefrom is directed toward the reflectivesurface 104 or toward the polarization plate 108.

The reflective surface 104 reflects at least a portion of the light fromthe light source 102 toward the polarized display panel 106 and thepolarization plate 108. The light may change polarization whenreflected. The reflective surface 104 may be made of a material capableof reflecting light or may be a coated with a reflective material.Suitable materials include, but are not limited to materials that may besmooth and white, or may have a mirrored surface. To maximize usage oflight from the light source 102, the reflective surface 104 may be partof an inner surface of an enclosure 112 configured to form a cavity intowhich the light is injected. While a simple box-like cavity is depictedin FIG. 1, other conventional cavities such as edgelit cavities may alsobe used. In an edgelit cavity the reflective surface 104 may furtherinclude a transparent light guide to aid in evenly distributing light.

The polarized display panel 106 is spaced apart from the light source102 and the reflective surface 104 and is configured to receive aportion of the light therefrom. In an embodiment, the polarized displaypanel 106 has a predetermined polarization axis 114 so that passage islimited to incident light polarized in a particular orientation that issubstantially aligned with the predetermined polarization axis 114. Inthis regard, the polarized display panel 106 may be an active matrixliquid crystal display, super twisted nematic liquid crystal display,ferroelectric liquid crystal display, or other light modulator capableof manipulating the polarization of light. In many such displays, thepolarization axis 114 may represent a polarization plane as is wellunderstood in the art. In these cases, the polarization axis 114 shownmay be the intersection of the polarization plane and the surface plane,and may correspond to the electric field vector of normally incidentlight for which passage is allowed.

The polarized display panel 106 may additionally include a rearpolarizer 116 disposed on one side. The rear polarizer 116 may beconfigured to ensure that light entering the polarized display panel 106is aligned with the predetermined polarization axis 114. In anotherembodiment, the polarized display panel 106 may also include a frontpolarizer 118 disposed on the opposite side. The front polarizer 118 mayfurther filter light to enhance clarity or contrast for a viewer of thedisplay 100. In this regard, the front polarizer 118 may operate byallowing passage of light aligned with a polarization axis, which may ormay not be substantially similar to the predetermined polarization axis114 of the rear polarizer 116.

In any case, before light is received by the polarized display panel106, it passes through the polarization plate 108. The polarizationplate 108 may be attached along its perimeter to the enclosure 112.Attachment may be provided, for example, by mechanical fixturing whichminimizes light leakage around the perimeter of the attachment region.In an embodiment, a central area of polarization plate 108 may not bedirectly attached to the enclosure 112, the reflective surface 104 orthe light source 102, and may be separated from those components by alow refractive index medium such as air. The polarization plate 108 isconfigured to diffuse and to prepolarize at least a portion of theincident light from the light source 102 and the reflective surface 104before it reaches the polarized display panel 106. In an embodiment, thepolarization plate 108 prepolarizes the light in a predeterminedorientation that is substantially aligned with the predeterminedpolarization axis 114 and is configured to allow passage of such lighttherethrough. In another embodiment, to increase energy efficiency ofthe display device 100 the polarization plate 108 may additionally beconfigured to continuously recycle a portion of the light that is notsuitably aligned with the predetermined polarization axis 114 until itis re-oriented and aligned substantially similarly to the predeterminedpolarization axis 114 and allowed to pass through to the polarizeddisplay panel 106.

FIG. 2 is a cross-sectional view of the polarization plate 108 that maybe implemented into the display device 100 shown in FIG. 1, according toan embodiment. The polarization plate 108 is a unitary structure havinga first major surface 109, a second major surface 111 opposite the firstmajor surface 109, and an edge 113. The first and second major surfaces109, 111 are joined together by the edge 113. In an embodiment, thefirst major surface 109 is configured to allow a majority of incidentlight from the light source and from the reflective surface 104 to betransmitted therethrough toward the second major surface 111.

The polarization plate 108 also includes a repolarization region 120 anda prepolarization region 122, each disposed between the first and secondmajor surfaces 109, 111. The repolarization region 120 is configured todiffuse and to depolarize or rotate at least one plane of polarizationof the light passing therethrough. In one embodiment, the repolarizationregion 120 may have a thickness that allows it to be a semi-rigid andself-supporting structure. In this embodiment, the repolarization region120 may be configured to have properties similar to those of a volumediffuser, allowing a portion of the incident light to be passed orforward-scattered and a portion of the incident light to beback-scattered. For example, the repolarization region 120 may have amicroscopically varying refraction index throughout.

In another embodiment, the repolarization region 120 may be configuredto diffuse light in a manner similar to that of a surface diffuser. Inan example, the repolarization region 120 may have a substantiallyuniform birefringent refraction index throughout and may include asurface texture on a surface. In yet another embodiment, therepolarization region 120 may be relatively thin and flexible, such as afilm.

The prepolarization region 122 receives the light that has passedthrough the repolarization region 120. In an embodiment, theprepolarization region 122 is configured to further filter the passedlight by allowing passage of light having a plane of polarization thatis substantially aligned with the predetermined polarization axis 114and preventing passage of light having a plane of polarization that isnot substantially aligned with the predetermined polarization axis 114.To further enhance energy efficiency, the prepolarization region 122 maybe a non-absorbing structure. For example, the prepolarization region122 may be configured to specularly reflect light or to backscatterlight which is not substantially aligned with the predeterminedpolarization axis 114. Although the prepolarization region 122 is shownin FIG. 2 as having an exterior surface interfacing with air, any othermedium may be in contact therewith. For example, the prepolarizationregion 122 may include an absorbing polarizer (not shown) adjacentthereto. The absorbing polarizer may have a polarization axis that issubstantially similar to the predetermined polarization axis 114 of theprepolarization region 122 and may be attached as rear polarizer 116 ofdisplay panel 106.

Some examples of suitable structures that may be implemented into theprepolarization region 122 are shown in FIGS. 3-6. In an embodimentshown in FIG. 3, the prepolarization region 122 may be a backscatteringuniaxial structure that includes liquid crystal droplets 302 dispersedin a polymer matrix 304. The liquid crystal droplets 302 may behomogeneously aligned in the polymer matrix 304 and may be separate orinterconnected, and with either symmetrical or nonsymmetrical shapes.The particular liquid crystal from which the droplets 302 are made maybe selected such that either an ordinary or extraordinary refractiveindex thereof matches a corresponding refractive index of the polymermatrix 304. In an embodiment, alignment of the liquid crystal in thedroplets 302 may be induced physically, such as by stretching. Inanother embodiment, liquid crystal alignment may be induced by applyingan electric or a magnetic field in an appropriate field direction, viafor example, optional electrodes 306. In another embodiment consistentwith FIG. 3, regions 302 may instead represent polymer domains with arefractive index matching the refractive index of polymer matrix 304 fora first polarization axis and with a refractive index mismatch for asecond polarization axis.

In still another backscattering embodiment, as shown in FIG. 4, theprepolarization region 122 may include transparent fibers 402 that arealigned with each other and embedded in a polymer matrix 404. Thetransparent fibers 402 may or may not be birefringent. In the case ofbirefringent transparent fibers 402, a non-birefringent polymer matrix404 may be employed. In the case of non-birefringent transparent fibers(e.g., glass fibers), a birefringent polymer matrix (e.g., polymericliquid crystal) may be used.

Another example of a suitable backscattering structure for theprepolarization region 122 is shown in FIG. 5. In this embodiment, theprepolarization region 122 may include birefringent crystals 502 thatthat are aligned along an axis 504. The birefringent crystals 502 may beembedded in a non-birefringent polymer matrix 506.

According to another embodiment, shown in FIG. 6, the prepolarizationregion 122 may be made up of alternating layers 602 and 604 of polymermaterials having differing birefringence. Here, the refractive index oflayers 602 and layers 604 are substantially matched for a firstpolarization axis and are a mismatch for a second polarization axis.

In one exemplary embodiment, the prepolarization region 122 may beconfigured to have characteristics that are similar to those of theVIKUITI™ Diffuse Reflective Polarizer Films available through 3MCorporation of St. Paul, Minnesota. In another embodiment, theprepolarization region 122 may be configured to operate similarly to aVIKUITI™ Dual Brightness Enhancement Film available through 3MCorporation of St. Paul, Minnesota. Other non-absorbing polarizers mayalso be used, including but not limited to cholesteric structures andwire-grid polarizing structures.

Referring again to FIG. 2, the two regions 120, 122 may be in contactwith each other or adhered to each other in any suitable manner. Forexample, if the repolarization region 120 is semi-rigid and theprepolarization region 122 is flexible, the prepolarization region 122may be laminated directly onto the repolarization region 120. In thecase of a flexible repolarization region 120 and a semi-rigidprepolarization region 122, the two regions 120, 122 may for example belaminated to each other or the repolarization region 120 may be appliedto the prepolarization region 122 as a coating. In an embodiment inwhich the repolarization region 120 and the prepolarization region 122are both flexible, the two regions 120, 122 may be laminated to eachother or coextruded with one another. Alternatively, the repolarizationregion 120 may be coated with material suitable for forming theprepolarization region 122. In another embodiment, the two regions 120,122 are formed as a continuously graded structure.

In still another embodiment, as shown in FIG. 7, the polarization plate108 may include an interface 124 that is disposed or formed between thetwo regions 120, 122. The interface 124 may be a transparent materialhaving a refractive index that is substantially similar to that of therepolarization region 120 and the prepolarization region 122. In anotherembodiment, the interface 124 may be configured to modulate at least oneplane of polarization of the light from a first orientation to a secondorientation. For example, in an embodiment, the interface 124 may beconstructed similarly to a quarterwave retarder, and the repolarizationregion 120 may be configured to preserve polarization. In such case, therepolarization region 120 and the interface 124 cooperate to accomplishpolarization rotation.

The interface 124 may serve as a semi-rigid structure to which aflexible repolarization region 120 and a flexible prepolarization region122 are adhered. In such case, the repolarization region 120 and theprepolarization region 122 may be laminated onto the interface 124.Alternatively, suitable materials forming the repolarization region 120and the prepolarization region 122 may be used to coat each side of theinterface 124. In an embodiment, each of the repolarization region 120,the prepolarization 122, and the interface 124, if included, may besubstantially uniform in thickness and construction along the directionsperpendicular to the display panel 106 normal.

FIG. 8 is a simplified illustration of an embodiment of lightpropagating through a polarization plate 108. In this embodiment, thepolarization plate 108 includes adjacent repolarization andprepolarization regions 120, 122 that are substantially index-matched atthe interface 124. The repolarization and prepolarization regions 120,122 are both configured to diffuse light. However, the repolarizationregion 120 is further configured to receive polarized light from theprepolarization region 122 and return substantially unpolarized orrandomly polarized light to the prepolarization region 122, while theprepolarization region 122 is further configured to allow passage oflight polarized along a predetermined axis substantially undeflected andbackscatter light polarized along another axis.

Light is injected through the first major surface 109 and not betweenthe repolarization and prepolarization regions 120, 122 or thepolarization plate edge 113. When the light passes through therepolarization region 120, some light rays 130 may be incident upon asubregion 132 of the repolarization region 120. Although the light rays130 are shown as coming from a single direction, for example from thelightsource 102 or reflective surface 104, both of FIG. 1, it will beappreciated that the light rays 130 may include other rays incident uponthe subregion 132 from more than one direction. The light rays 130 mayalso include those from adjacent subregions 134 and others not shown.The subset of light rays 130 which arrive from the lightsource 102 orreflective surface 104 may be incident through a first major surface 109of the polarization plate 108. The first major surface 109 may interfacewith air.

The subregion 132 may scatter the light rays 130 having randompolarization in random directions. For example, in an embodiment, afirst portion of the light rays 138 are scattered from the subregion 132in the general direction of and with a polarization matching thepolarization axis of the prepolarization region 122. The first portionof the light rays 138 may then reach a second major surface 111 of thepolarization plate 108 with an angle of incidence which allows themajority of the light energy to refract into the exterior medium, suchas air. This portion is well suited to match the predeterminedpolarization axis 114 of FIG. 1. A second portion of the light rays 142is scattered from the subregion 132, but has a polarization that may bebackscattered by the prepolarization region 122. In such case, amajority of the light energy associated with the second portion of thelight rays 142 may be returned to the repolarization region 120 in theform of backscattered rays 144 without reaching the second major surface111.

A third portion of the light rays 146 may exit the subregion 132 with apolarization which may be transmitted by the prepolarization region 122but that may exceed a critical or acceptable angle for refraction out ofthe polarization plate 108. As a result, the third portion of the lightrays 146 may be reflected via total internal reflection (“TIR”) backtoward the repolarization region 120. The light energy in the thirdportion of the light rays 146 may then return to repolarization region120, for example to adjacent subregions 134, for another opportunity toscatter and exit the repolarization region 120 in a manner similar tothe first portion of light rays 138. In one embodiment, a furtherportion of the light rays 148 are backscattered and exit therepolarization region 120 in a direction opposite that of theprepolarization region 122.

In another embodiment, a portion of the light rays 150 undergo TIR atthe first major surface 109 of the polarization plate 108. Such a resultmay occur when an angle of incidence of the returned light rays 150 (orother light rays) with respect to the corresponding interface surfacenormal exceeds a critical angle for TIR. In either case involving TIR,the critical angle for TIR at a substrate-to-air boundary (“air criticalangle”), such as the boundary between air 154 and the first or secondmajor surfaces 109, 111 of the polarization plate 108, may vary with aparticular refractive index of the material from which the particularregion may be made. For example, optical materials such as plastic orglass typically exhibit an air critical angle in the range of 27 degrees(n=2.2) to 49 degrees (n=1.33). For materials having a refractive indexof n=1.5, such as certain common glass or plastic materials, the aircritical angle may be about 42 degrees from normal. In the embodiment ofFIG. 8, it is evident that light, for example portions of light rays142, 144 and 146, passes between repolarization region 120 andprepolarization region 122 and through the interface 124 at angles whichexceed the air critical angles for the materials in the correspondingregions.

The polarization plate 108 described above may provide increasedluminance from various viewing angles when compared to conventionalliquid crystal displays including a diffuser, a pre-polarizing film, anda rear polarizer separated from each other by airgaps. In one particularexperiment, relative luminance was measured over a range of horizontalviewing angles while maintaining a vertical viewing angle of 0 degrees.The relative luminance was then plotted onto a graph 900, shown in FIG.9. Data representing relative luminance of a conventional liquid crystaldisplay with a pre-polarizing film is shown as line 902, while datarepresenting relative luminance of a liquid crystal display includingthe polarization plate 108 is shown as line 904. As shown in the graph900, the liquid crystal display including the polarization plate 108 hasincreased luminance over that of the conventional device, especially atwide viewing angles. Direct comparisons with laminated assemblies ofnon-diffuse layers are not meaningful, as the presence of diffusionintroduces complex interactions as was exemplified in FIG. 8. Forexample, rather than simple improvement as might be associated withelimination of surface reflections, previous findings in which diffuserswere laminated directly to rear polarizers have shown overall reductionof efficiency.

In addition to increasing efficiency of the display device 100, theinclusion of the polarization plate 108 may reduce overall size and/orthickness of the display device 100. Additionally, display devices thatinclude the polarization plate 108 may be more structurally robust thanconventional display devices having comparable functionality.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the inventive subject matter, itshould be appreciated that a vast number of variations exist. It shouldalso be appreciated that the exemplary embodiment or exemplaryembodiments are only examples, and are not intended to limit the scope,applicability, or configuration of the inventive subject matter in anyway. Rather, the foregoing detailed description will provide thoseskilled in the art with a convenient road map for implementing anexemplary embodiment of the inventive subject matter. It beingunderstood that various changes may be made in the function andarrangement of elements described in an exemplary embodiment withoutdeparting from the scope of the inventive subject matter as set forth inthe appended claims.

What is claimed is:
 1. A component for use between a light source and adisplay panel of a liquid crystal display, the component comprising: aplate consisting of a first layer and a second layer, the plateincluding a first major surface, a second major surface opposing thefirst major surface, and an edge joining the first and second majorsurfaces, the first major surface configured to allow a majority ofincident light from a light source to be transmitted therethrough anddefining a first side of the first layer, the second major surfaceconfigured to receive a portion of the transmitted incident light fromthe first layer and defining a first side of the second layer, wherein:the first layer is a single, discrete structure having a microscopicallyvarying refraction index, the first layer adapted to diffuselybackscatter a portion of incident light entering the first layer and todepolarize a plane of polarization of the portion of incident lightpassing through the first layer, the second layer is in contact with andadjacent to the first layer and is configured to be substantiallyindex-matched to the first layer and substantially nonabsorbent to allowpassage of light through the second major surface having a plane ofpolarization that is substantially aligned with a predeterminedpolarization axis of the display panel, and to substantially preventpassage of light through the second major surface having a plane ofpolarization that is not substantially aligned with the predeterminedpolarization axis of the display panel, incident light is not injectedbetween the first layer and the second layer and is not injected throughthe plate edge, and incident light reaching the second layer but notpassing through the second major surface is returned to the first layerwhere a portion of the returned incident light is depolarized anddiffusely backscattered in the first layer and directed toward thesecond layer.
 2. The component of claim 1, wherein the first majorsurface of the plate has a texture formed thereon.
 3. The component ofclaim 1, wherein the second layer is further configured to diffuselight.
 4. The component of claim 1, wherein the second layer is furtherconfigured to reflect light.
 5. The component of claim 1, wherein thesecond layer is further configured to backscatter light.
 6. A componentfor use between a light source and a display panel of a liquid crystaldisplay, the component comprising: a plate consisting of a first layerand a second layer bonded together to form a single structure having afirst major surface, a second major surface opposing the first majorsurface, and an edge joining the first and second major surfaces, thefirst major surface configured to allow a majority of incident lightfrom a light source to be transmitted therethrough and defining a firstside of the first layer, the second major surface configured to receivea portion of the transmitted incident light from the first layer anddefining a first side of the second layer, the second major surfacebeing adjacent to air, wherein: the first layer is a single film havinga microscopically varying refraction index, the first layer adapted todiffusely backscatter a portion of incident light entering the firstlayer and to depolarize a plane of polarization of the portion ofincident light passing through the first layer, the second layer islaminated over to be in contact with and adjacent to the first layer andis a single film configured to be substantially index-matched to thefirst layer and substantially nonabsorbent to allow passage of lightthrough the second major surface having a plane of polarization that issubstantially aligned with a predetermined polarization axis of thedisplay panel, and to substantially prevent passage of light through thesecond major surface having a plane of polarization that is notsubstantially aligned with the predetermined polarization axis of thedisplay panel, incident light is not injected between the first layerand the second layer and is not injected through the plate edge, andincident light reaching the second layer but not passing through thesecond major surface is returned to the first layer where a portion ofthe returned incident light is depolarized and diffusely backscatteredin the first layer and directed toward the second layer.
 7. A displaydevice, comprising: a light source; a reflective surface disposedproximate the light source and configured to reflect light emittedtherefrom; a polarized display panel spaced apart from the reflectivesurface, the polarized display panel having a predetermined polarizationaxis; and a plate disposed between the reflective surface and thepolarized display panel and configured to receive the reflected light,the plate consisting of a first layer and a second layer, the plateincluding a first major surface, a second major surface opposing thefirst major surface, and an edge joining the first and second majorsurfaces, the first major surface configured to allow a majority of thereflected light to be transmitted therethrough and defining a first sideof the first layer, the second major surface configured to receive aportion of the reflected light from the first layer and defining a firstside of the second layer, wherein: the first layer is a single, discretestructure having a microscopically varying refraction index, the firstlayer adapted to diffusely backscatter a portion of the reflected lightentering the first layer and to depolarize a plane of polarization ofthe reflected light passing through the first layer, the second layer isin contact with and adjacent to the first layer and is configured to besubstantially index-matched to the first layer and substantiallynonabsorbent to allow passage of light through the second major surfacehaving a plane of polarization that is substantially aligned with apredetermined polarization axis, and to substantially prevent passage oflight through the second major surface having a plane of polarizationthat is not substantially aligned with the predetermined polarizationaxis, incident light is not injected between the first layer and thesecond layer and is not injected through the plate edge, and thereflected light reaching the second layer but not passing through thesecond major surface is returned to the first layer where a portion ofthe returned reflected light is depolarized and diffusely backscatteredin the first layer and directed toward the second layer.